1. Field of the Invention
The present invention relates to photolithography, and particularly to an overlay control system and an overlay control method for an exposure tool, and a manufacturing method for a semiconductor device.
2. Description of the Related Art
In the manufacture of semiconductor devices and the like, a plurality of material layers are formed atop a semiconductor substrate by a plurality of processes. For example, in photolithography, a mask pattern of a process target layer is transferred onto a resist film coated on the semiconductor substrate. The mask pattern of the process target layer is aligned with an underlying pattern formed in an underlying layer. In order to ensure overlay accuracy with respect to the underlying layer, a control set value is assigned to an exposure tool so as to control an overlay for alignment of the mask pattern with the underlying pattern.
In controlling a typical overlay, an overlay correction value is used as a control set value of an exposure tool (refer to Japanese Unexamined Patent Application Publication No. H11-260683). The overlay correction value is calculated based on a result of an overlay inspection carried out to an underlying layer as an overlay target. In controlling a typical overlay, the overlay accuracy to the overlay target underlying layer can be improved. However, it is impossible to satisfy the overlay accuracy with respect to other underlying layers simultaneously. In addition, the overlay accuracy may be defined with respect to each direction orthogonal to one another, for example, an X direction and a Y direction, depending on the structure of the semiconductor device. In a case in which the overlay accuracy of each of the X and the Y directions is defined independently with respect to different underlying layers, the typical overlay control cannot be utilized.